Apparatus for detecting dilution or commingling of substances



Patented July 5, 1949 APPARATUS FOR DETECTING lllLUTION B COMMINGLING 0FSUBSTANCES Henry L. Grimes. Winchester, Mm.

Application May 14, 1947, Serial No. 747,922

This application is a continuation in part of my prior applicationSerial No. 591,715, illed May 3, 1945, now abandoned.

The invention relates to a device for detecting dilution or comminglingof substances, and is particularly concerned with an improvedelectronic-type detector which, for example, may serve to give a warningto an aircraft pilot or other operator of the presence in engine fuel ofharmful quantities of water or other fluids affecting the combustibleproperties of the fuel.

An object of the invention is to provide an effective and dependabledetector or sensing apparatus which will give a visual and/or audibleindication to an operator of the condition of liquid fuel or other fluidflowing through a conduit or passage.

Another object is to provide a device of the type specified utilizing aprobe or the like which is affected by the diilerent specificresi'stances of different substances, the probe being interposed in a D.C. electric circuit unusually sensitive to any change in conductance-and embodying means whereby the change is indicated by a suitablesignal.

Another object is to provide an electronic device for detecting in afluid such as gasoline having a given specific resistance the presenceof another fluid such as water having a different specific resistance,the device being so constructed and arranged and capable of utilizingvoltages so low as to avoid any fire or explosion hazard.

A further object is to provide a device for detecting dilution orcommingling ofsubstances utilizing a probe and thermionic tube circuitof a dependable nature and which at the same time is relativelyinexpensive and will accommodate itself to a wide variety ofinstallation conditions.

The foregoing and other objects and advantages will become apparent inview .ofthe following description taken in conjunction with thedrawings, wherein: l

. Figure 1 is a diagrammatic representation of apparatus in accordancewitlrthe invention;

Figure 2 is a top plan view of the probe housing or chamber; 4 l

Figure 3 is a view in` elevation of the probe chamber, partly brokenaway to show the probe therein;

Figures 4, 4A and 4B arevviews in side and opposite end elevation,respectively, of a probe which may be usedin the circuit of Figure 1;and

Figure 5 is a perspective lview of the apparatus as it appears whenassembled in the housing or casing adapted therefor.

6 Claims. (Cl. 177-311) it is mounted in a housing or case 20, themilliam- The device consists oi a power transformer I, vacuum tube 2,withI its associated circuit, an indicating milliamrneter 3, and a relay4 which actuates green and red panel lamps 5 and 6. A resistor-capacitornetwork composed of two capacitors 1 and 8 and the interconnectedresistor 9 enables the use of a rather long connecting line between theinstrument and the probe I0 and insures reliable operation.

The power transformer I supplies for example volts A. C. to the platecircuit of the tube 2, 'and 6.3 volts A. C. to the heater of the tube 2.This 6.3 volts A. C. source is also used on the diode portion of thetube to provide a source of D. C. bias for the tube. The R. C. networkcomposed of the two capacitors 1 and 8 and the interconnected resistor 9filters the rectified bias voltage in addition to eliminating capacityeffect of long probe cables.

The resistor i I is the grid-cathode input resistor to establish a fixedgrid bias controlling tube emission under open circuit conditions at theprobe. The resistor l2 directly in the grid lead serves to limit gridcurrent and to partially isolate the grid from external eifects.

The plate circuit relay l hassingle pole, double throw contacts capableof handling several amperes of current; it is by-passed through acondenser i3 to avoid chatter and to raise the D. C. voltage across therelay.

The negative grid bias voltage is connected to the grid of the tubeIthrough the probe I0, which normally constitutes an open circuit. Thenormal bias on the tube is considerably less negative than the biasimposed when the probe circuit is closed.

In Figures 2 and 3 the probe I0 and its elements I0' and I0" is shown inits housing l5 which is open at the top at I8 and at oneend for fluidvflow. The positive and negative elements of the probe are indicated atI0 and I0" mounted in an insulating plug I4 and shown in Figures l and4A, the said elements being secured to an end plug I1 as best shown inFigures 4 and 4B and provided with terminals I8 and I9.

Figure 5 shows the unit in its commercial form;

meter 3 and red and green signal lights 5 and 8 being exposed on theface of the housing.

Operation A change in the conductivity of the substance being sampled bythe probe results in a change in the grid bias applied to the vacuumtube. Consequently, the plate current changes, producing a correspondingcomparative change in the reading on the indicating milliammeter, and incases where substances pass a critical conductance, producing relayaction which extinguishes the green lamp and illuminates the red lamp.Opera-v tion of the relay may also be employed to give an audiblesignal.

The initial bias on the grid being very small, maximum plate currentexists, the relay 4 is energized, the milliammeter 3 reads or indicatesthe value of the plate current; the probe circuit to the grid beingopen, the green lamp is illuminated.

A change in the conductivity of the substance being probed, whether itbe gasoline or lumber being dried in a kiln by way of examples, willresult in a change in the grid bias which will change the plate current.In the case of gasoline mixed with water the plate current goes frommaximum to minimum. In the case of lumber being dried in a kiln, theplate current goes from minimum to maximum. The red lamp 6 isilluminated at minimum plate current and the green lamp 5 is illuminatedat maximum plate current. Interpolations between minimum and maximumplate currents are read from the indicating milliammeter 3. Theseinterpolations for instance would apprise a kiln operator in a furnituremanufacturing plant when the charge of lumber in the kiln is ready to beremoved.

It should be noted that when the unit is rst plugged into the source ofpower supply, the red lamp 6 will immediately be illuminated, and themilliammeter will read zero. When the tube has warmed up, themilliammeter will start going up scale provided the probe circuit .tothe grid is open or is in intimate contact with a substance of lowconductivity. After a few seconds the milliammeter will read full platecurrent. The relay will pull in when itis slightly more than half-scale,switching ofi the red lamp and switching on the green lamp. The unit isnow ready for operation.

The instrument may be remotely located and connected to the probe bymeans of an electrical cable. The tube input circuit contains a lternetwork, consisting of a resistor-capacitor network composed of twocapacitors 'l and 8 and the inter-connected resistor 9, enabling the useo1' a rather long line between the instrument and the probe. It alsoinsures reliable operation.

Tests have been made with methyl alcohol, kerosene, amyl alcohol,benzine, ethyl alcohol, ordinary motor gasoline 72 octane, and aviationgasoline 93 octane. All tests have shown conclusively when pure uid waspassing through the plates of the probe and when water passed throughthe plates of the probe with the iiuid.

The probe may be designed to meet conditions of use and installation.Thus in testing certain substances or materials the probe may take theform of spaced conducting elements adapted to move over or through thesubstance or on opposed surfaces oi the material.

It will also be understood that parts may be substituted and re-arrangedin the respective circuits as well as changes made in construction anddesign within the scope of the invention as dened by the appendedclaims.

What I claim as new is:

1. Apparatus for detecting variations in the electrical conductiveproperties of iluids, comprising a primary electric circuit, a source ofelectrical energy such as a transformer, a rectifying circuit includinga vacuum tube having a grid circuit, a plate circuit and a source ofdirect current for the grid circuit, a probe in said primary circuit inseries with the grid circuit of said tube, said probe having spacedconductive elements adapted to be located in the iluid so that changesin the conductive properties of the iiuid result in a change in theresistance of the primary circuit, a signal circuit including a relayand a relay coll connected into the plate circuit, and a capacitorconnected across the coil providing a low-resistance path for thealternating current in the plate circuit, the direct current componentin the plate circuit operating the relay upon attaining a valuedetermined by the resistance in the primary circuit.

2. Apparatus for detecting in a substance having a given specificresistance the presence oi another substance having a different speciiicresistance including a primary circuit, a rectifying circuit including avacuum tube having a grid and associated grid circuit and a plate andassociated plate circuit energized from a source of power, a probe inseries with said grid circuit, said probe having spaced conductiveelements adapted to be located in contact with the substance undergoingtest so that changes in the conductive properties of the substancesresult in a change in the conductance of the primary circuit, a signalcircuit including a relay and a relay coil connected into the platecircuit and a capacitor connected across the coil providing a lowresistance path for the alternating current in the plate circuit, thedirect current component in the plate circuit operating the relay uponattaining a value determined by the resistance of the primary circuit,and means for compensating for capacity effect of long lines connectinginn strument probe including a resistor-capacitor network for insuringreliable operation.

3. Apparatus for detecting in a substance having a given speciiicresistance the presence of another substance having a differentresistance including a primary circuit, a rectifying circuit including avacuum tube having a grid and associated grid circuit and a plate andassociated plate circuit energized from a source of power, a probe inseries with said grid circuit, said probe having spaced conductiveelements adapted to be located in contact with the substance undergoingtest so that changes in the conductive prop-` erties of the substancesresult in a change in the conductance of the primary circuit, a signalcircuit including a relay and a relay coil connected into the platecircuit and a capacitor connected across the coil providing a lowresistance path for the alternating current in the plate circuit, thedirect current component in the plate circuit operating the relay uponattaining a value determined by the resistance of the primary circuit,means for compensating for capacity effect of long lines connectinginstrument probe including a resistor-capacitor network which insuresreliable operation, said relay coil capacitor functioning to assurepositive operation of the relay by the direct current component of theplate circuit current by bleeding oif the alternating current componentof the plate circuit current through said low resistance path inparallel with the said relay coil.

4. Apparatus for detecting in a substance having a given specificresistance the presence of another substance having a different specificresistance including a primary circuit, a rectifying circuit including avacuum tube having a grid and associated grid circuit and a plate andassociated plate circuit energized from a source of power, a probe inseries with said grid circuit, said probe having spaced conductiveelements adapted to be located in contact With the substance undergoingtest so that changes in the conductive properties of the substancesresult in a change in the conductance of the primary circuit, a signalcircuit including a relay and a relay coil connected into the platecircuit and a capacitor connected across the coil providing a lowresistance path for the alternating current in the plate circuit, thedirect current component in the plate circuit operating the relay uponattaining a value determined by the resistance of the primary circuit,means for compensating for capacity eiect of long lines connecting theinstrument probe including a resistor-capacitor network which insuresreliable operation, said relay coil capacitor functioning to assurepositive operation of the relay by the direct current component of theplate circuit current by bleeding off the alternating current componentof the plate circuit current through said loW resistance path inparallel with said relay coil, and means to determine interpolativereadings of the apparatus including a milliamrneter connected in theplate circuit in series With the relay coil.

5. Apparatus for detecting in a substance having a given specificresistance the presence of another substance having a different specificresistance including a primary circuit, a rectifying circuit including avacuum tube having a grid and associated grid circuit and a plate `andassociated plate circuit energized from a source of power, a probe inseries with said grid circuit, said probe comprising a pair of spacedconductive elements adapted to be located in contact with the substanceundergoing test so that changes in the conductive properties of thesubstances result in a change in the conductance of the pri- -marycircuit, a signal circuit including a relay and a relay coil connectedinto the plate circuit and a capacitor connected across the coilproviding a low resistance path for the alternating current in the platecircuit, the direct current component in the plate circuit' operatingthe relay upon attaining a value determined by the resist'- ance of theprimary circuit, means for compensating for capacity eifect of longlines connecting the instrument probe including a resistor-capacitornetwork which insures reliable operation, said relay coil capacitorfunctioning to assure positive operation of the relay by the directcurrent component of the plate circuit current by bleeding off thealternating current component of the plate circuit current through saidlow resistance path in parallel with said relay coil, means to determineinterpolative readings of the apparatus including a milliammeterconnected in the plate circuit in series with the relay coil, said relaybeing responsive to direct currents of a given magnitude.

6. Apparatus for detecting in a substance having a given specificresistance the presence of another substance having a different speciiicresistance including a primary circuit, a rectifying circuit including avacuum tube having a grid and associated grid circuit and a plate andassociated plated circuit energized from a source of power, a probe inseries with said grid circuit, said probe comprising a pair of spacedconductive elements adapted to be located in contact with the substanceundergoing test so that changes in the conductive properties of thesubstances result in a change in the conductance of the primary circuit,a signal circuit including a relay and a relay coil connected into theplate circuit and a capacitor connected across the coil providing a lowresistance path for the alternating current in the plate circuit, thedirect current component in the plate circuit operating the relay uponattaining a Value determined by the resistance of the primary circuit,means for compensating for capacity effect of long lines connecting theinstrument probe including a resistor-capacitor network arranged tofilter the rectified bias voltage, said relay coil capacitor functioningto assure positive operation of the relay by the direct currentcomponent of the plate circuit current by bleeding oif the alternatingcurrent component of the plate circuit current through said lowresistance path in parallel with said relay coil, means to determineinterpolative readings of the apparatus including a milliammeterconnected in the plate circuit in series with the relay coil, said relayoperating as the result of changes in the specific resistances of theiiuids undergoing test and being responsive to direct currents of agiven magnitude, means for utilizing the effect of electrical signals onthe relay including a signal circuit connected to the contacts andarmature of said relay and having an indicating signal therein, and asource of electrical energy such as a transformer.

HENRY L. GRIMES.

REFERENCES CITED UNITED STATES PATENTS Name Date Ewertz May 28. 1940Number

